Final answer:
Use mental math to solve addition problems by rounding and adding the rounded numbers. The thinking differs based on whether you round up or down.
Step-by-step explanation:
To solve these addition problems using mental math, you can break down the numbers into smaller, easier-to-work-with parts. For example, to solve 1,289 + 1,566, you can round each number to the nearest hundred and then add the rounded numbers. 1,289 rounded to the nearest hundred is 1,300, and 1,566 rounded to the nearest hundred is 1,600. Now you can mentally add 1,300 + 1,600, which is 2,900.
For the equation 1,034 + 1,566, you can again round each number to the nearest hundred. 1,034 rounded to the nearest hundred is 1,000, and 1,566 rounded to the nearest hundred is 1,600. Now you can mentally add 1,000 + 1,600, which is 2,600.
The thinking is different in the two cases because in the first equation, you're rounding up to the nearest hundred, while in the second equation, you're rounding down to the nearest hundred. This affects the final result.
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